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Add docs for IDE0121, IDE0340, IDE0350 (#45510)
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‎docs/fundamentals/code-analysis/style-rules/ide0121.md

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---
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title: "IDE0121: Simplify LINQ type check and cast"
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description: "Learn about code analysis rule IDE0121: Simplify LINQ type check and cast"
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ms.date: 03/25/2025
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f1_keywords:
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- IDE0121
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helpviewer_keywords:
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- IDE0121
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dev_langs:
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- CSharp
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---
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# Simplify LINQ type check and cast (IDE0121)
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| Property | Value |
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|--------------------------|-------------------------------------------------------|
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| **Rule ID** | IDE0121 |
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| **Title** | Simplify LINQ type check and cast |
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| **Category** | Style |
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| **Subcategory** | Unnecessary code rules (expression-level preferences) |
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| **Applicable languages** | C# and Visual Basic |
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## Overview
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This rule flags LINQ expressions where the type of elements of a sequence are checked (by calling <xref:System.Linq.Enumerable.Where``1(System.Collections.Generic.IEnumerable{``0},System.Func{``0,System.Boolean})>) and then cast to that type (by calling either <xref:System.Linq.Enumerable.Cast``1(System.Collections.IEnumerable)> or <xref:System.Linq.Enumerable.Select``2(System.Collections.Generic.IEnumerable{``0},System.Func{``0,``1})>). The code fixer converts these expressions to call <xref:System.Linq.Enumerable.OfType``1(System.Collections.IEnumerable)> instead.
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## Options
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This rule has no associated code-style options.
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## Example
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```csharp
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// Code with violations.
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IEnumerable<int> y = objects.Where(a => a is int).Cast<int>();
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IEnumerable<int> z = objects.Where(a => a is int).Select(a => (int)a);
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// Fixed code.
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IEnumerable<int> y = objects.OfType<int>();
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IEnumerable<int> z = objects.OfType<int>();
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```
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## Suppress a warning
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If you want to suppress only a single violation, add preprocessor directives to your source file to disable and then re-enable the rule.
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```csharp
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#pragma warning disable IDE0121
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// The code that's violating the rule is on this line.
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#pragma warning restore IDE0121
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```
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To disable the rule for a file, folder, or project, set its severity to `none` in the [configuration file](../configuration-files.md).
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```ini
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[*.{cs,vb}]
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dotnet_diagnostic.IDE0121.severity = none
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```
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To disable all of the code-style rules, set the severity for the category `Style` to `none` in the [configuration file](../configuration-files.md).
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```ini
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[*.{cs,vb}]
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dotnet_analyzer_diagnostic.category-Style.severity = none
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```
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For more information, see [How to suppress code analysis warnings](../suppress-warnings.md).
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## See also
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- [Language rules](language-rules.md)
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- [Code style rules reference](index.md)

‎docs/fundamentals/code-analysis/style-rules/ide0340.md

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---
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title: "IDE0340: Use unbound generic type"
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description: "Learn about code analysis rule IDE0340: Use unbound generic type"
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ms.date: 03/25/2025
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f1_keywords:
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- IDE0340
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helpviewer_keywords:
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- IDE0340
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dev_langs:
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- CSharp
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---
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# Use unbound generic type (IDE0340)
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| Property | Value |
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|--------------------------|------------------------------------------------------|
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| **Rule ID** | IDE0340 |
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| **Title** | Use unbound generic type |
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| **Category** | Style |
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| **Subcategory** | Language rules (expression-level preferences) |
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| **Applicable languages** | C# 14+ |
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| **Options** | `csharp_style_prefer_unbound_generic_type_in_nameof` |
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## Overview
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This rule flags places where the operand of a [nameof expression](../../../csharp/language-reference/operators/nameof.md) is a bound generic type (for example, `List<int>`). The code fixer offers to convert the operand to an unbound type (for example, `List<>`).
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## Options
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Options specify the behavior that you want the rule to enforce. For information about configuring options, see [Option format](language-rules.md#option-format).
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### csharp_style_prefer_unbound_generic_type_in_nameof
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| Property | Value | Description |
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|--------------------------|----------------------------------------------------|-----------------------------------------|
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| **Option name** | csharp_style_prefer_unbound_generic_type_in_nameof | |
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| **Option values** | `true` | Prefer unbound generic type in `nameof` expression |
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| | `false` | Disables the rule |
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| **Default option value** | `true` | |
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## Example
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```csharp
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// Code with violations.
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string name = nameof(List<int>);
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```
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```csharp
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// Fixed code.
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string name = nameof(List<>);
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```
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## Suppress a warning
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If you want to suppress only a single violation, add preprocessor directives to your source file to disable and then re-enable the rule.
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```csharp
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#pragma warning disable IDE0340
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// The code that's violating the rule is on this line.
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#pragma warning restore IDE0340
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```
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To disable the rule for a file, folder, or project, set its severity to `none` in the [configuration file](../configuration-files.md).
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```ini
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[*.{cs,vb}]
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dotnet_diagnostic.IDE0340.severity = none
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```
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To disable all of the code-style rules, set the severity for the category `Style` to `none` in the [configuration file](../configuration-files.md).
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```ini
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[*.{cs,vb}]
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dotnet_analyzer_diagnostic.category-Style.severity = none
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```
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For more information, see [How to suppress code analysis warnings](../suppress-warnings.md).

‎docs/fundamentals/code-analysis/style-rules/ide0350.md

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---
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title: "IDE0350: Use implicitly typed lambda"
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description: "Learn about code analysis rule IDE0350: Use implicitly typed lambda"
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ms.date: 03/25/2025
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f1_keywords:
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- IDE0350
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helpviewer_keywords:
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- IDE0350
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dev_langs:
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- CSharp
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---
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# Use implicitly typed lambda (IDE0350)
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| Property | Value |
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|--------------------------|----------------------------------------------------------|
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| **Rule ID** | IDE0350 |
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| **Title** | Use implicitly typed lambda |
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| **Category** | Style |
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| **Subcategory** | Language rules (expression-level preferences) |
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| **Applicable languages** | C# 14+ |
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| **Options** | `csharp_style_prefer_implicitly_typed_lambda_expression` |
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## Overview
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This rule flags places where an explicitly typed [lambda expression](../../../csharp/language-reference/operators/lambda-expressions.md) can be converted to an implicitly typed lambda expression.
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## Options
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Options specify the behavior that you want the rule to enforce. For information about configuring options, see [Option format](language-rules.md#option-format).
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### csharp_style_prefer_implicitly_typed_lambda_expression
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| Property | Value | Description |
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|--------------------------|--------------------------------------------------------|------------------------------------------|
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| **Option name** | csharp_style_prefer_implicitly_typed_lambda_expression | |
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| **Option values** | `true` | Prefer to use an implicitly typed lambda |
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| | `false` | Disables the rule |
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| **Default option value** | `true` | |
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## Example
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```csharp
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// Code with violations.
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Action<int> a = (int x) => { };
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Delegate b = (Action<int>)( (int x) => { } );
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```
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```csharp
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// Fixed code.
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Action<int> a = x => { };
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Delegate b = (Action<int>)( x => { } );
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```
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## Suppress a warning
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If you want to suppress only a single violation, add preprocessor directives to your source file to disable and then re-enable the rule.
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```csharp
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#pragma warning disable IDE0350
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// The code that's violating the rule is on this line.
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#pragma warning restore IDE0350
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```
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To disable the rule for a file, folder, or project, set its severity to `none` in the [configuration file](../configuration-files.md).
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```ini
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[*.{cs,vb}]
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dotnet_diagnostic.IDE0350.severity = none
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```
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To disable all of the code-style rules, set the severity for the category `Style` to `none` in the [configuration file](../configuration-files.md).
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```ini
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[*.{cs,vb}]
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dotnet_analyzer_diagnostic.category-Style.severity = none
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```
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For more information, see [How to suppress code analysis warnings](../suppress-warnings.md).

‎docs/fundamentals/code-analysis/style-rules/index.md

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> | [IDE0100](ide0100.md) | Remove unnecessary equality operator | |
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> | [IDE0110](ide0110.md) | Remove unnecessary discard | |
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> | [IDE0120](ide0120.md) | Simplify LINQ expression | |
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> | [IDE0121](ide0121.md) | Simplify LINQ type check and cast | |
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> | [IDE0130](ide0130.md) | Namespace does not match folder structure | [dotnet_style_namespace_match_folder](ide0130.md#dotnet_style_namespace_match_folder) |
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> | [IDE0140](ide0140.md) | Simplify object creation | [visual_basic_style_prefer_simplified_object_creation](ide0140.md#visual_basic_style_prefer_simplified_object_creation) |
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> | [IDE0150](ide0150.md) | Prefer `null` check over type check | [csharp_style_prefer_null_check_over_type_check](ide0150.md#csharp_style_prefer_null_check_over_type_check) |
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> | [IDE0306](ide0306.md) | Use collection expression for new | [dotnet_style_prefer_collection_expression](ide0306.md#dotnet_style_prefer_collection_expression) |
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> | [IDE0320](ide0320.md) | Make anonymous function `static` | [csharp_prefer_static_anonymous_function](ide0320.md#csharp_prefer_static_anonymous_function) |
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> | [IDE0330](ide0330.md) | Prefer 'System.Threading.Lock' | [csharp_prefer_system_threading_lock](ide0330.md#csharp_prefer_system_threading_lock) |
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> | [IDE0340](ide0340.md) | Use unbound generic type | [csharp_style_prefer_unbound_generic_type_in_nameof](ide0340.md#csharp_style_prefer_unbound_generic_type_in_nameof) |
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> | [IDE0350](ide0350.md) | Use implicitly typed lambda | [csharp_style_prefer_implicitly_typed_lambda_expression](ide0350.md#csharp_style_prefer_implicitly_typed_lambda_expression) |
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> | [IDE1005](ide1005.md) | Use conditional delegate call | [csharp_style_conditional_delegate_call](ide1005.md#csharp_style_conditional_delegate_call) |
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> | [IDE1006](naming-rules.md) | Naming styles | |
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‎docs/fundamentals/code-analysis/style-rules/language-rules.md

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- [Convert `typeof` to `nameof` (IDE0082)](ide0082.md)
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- [Remove unnecessary equality operator (IDE0100)](ide0100.md)
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- [Simplify LINQ expression (IDE0120)](ide0120.md)
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- [Simplify LINQ type check and cast (IDE0121)](ide0121.md)
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- [Namespace does not match folder structure (IDE0130)](ide0130.md)
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C# style rules:
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- [Use collection expression for builder (IDE0304](ide0304.md)
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- [Use collection expression for fluent (IDE0305)](ide0305.md)
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- [Use collection expression for new (IDE0306)](ide0306.md)
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- [Use unbound generic type (IDE0340)](ide0340.md)
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- [Use implicitly typed lambda (IDE0350)](ide0350.md)
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Visual Basic style rules:
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‎docs/navigate/tools-diagnostics/toc.yml

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href: ../../fundamentals/code-analysis/style-rules/ide0110.md
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- name: IDE0120
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href: ../../fundamentals/code-analysis/style-rules/ide0120.md
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- name: IDE0121
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href: ../../fundamentals/code-analysis/style-rules/ide0121.md
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- name: IDE0130
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href: ../../fundamentals/code-analysis/style-rules/ide0130.md
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- name: IDE0140
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href: ../../fundamentals/code-analysis/style-rules/ide0320.md
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- name: IDE0330
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href: ../../fundamentals/code-analysis/style-rules/ide0330.md
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- name: IDE0340
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href: ../../fundamentals/code-analysis/style-rules/ide0340.md
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- name: IDE0350
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href: ../../fundamentals/code-analysis/style-rules/ide0350.md
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- name: IDE1005
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href: ../../fundamentals/code-analysis/style-rules/ide1005.md
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- name: Miscellaneous rules

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